How are cervical selective nerve root blocks administered for pain management?

Updated: Jun 19, 2018
  • Author: Anthony H Wheeler, MD; Chief Editor: Meda Raghavendra (Raghu), MD  more...
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Answer

Answer

With the patient in the supine or lateral position on the fluoroscopy table, the fluoroscopy beam is rotated from a lateral to oblique position to allow visualization of the affected neural foramina at its largest diameter. Next, the fluoroscopy beam is moved from a cephalad to caudal position, which allows visualization of the affected neural foramen. This maneuver should place the beam parallel to the targeted nerve root in the approximate center of the inferior portion of the foramen.

Next, the skin is prepped with an antiseptic solution, and a skin wheal of local anesthetic is placed at a point overlying the posterior aspect of the foramen over the tip of the superior articular process of the level below the affected neural foramen. A 25-gauge, 2-inch needle is passed through the skin wheal and advanced until it abuts the superior articular process of the level below the targeted foramen. This contact on bone provides the operator with knowledge specifically regarding the depth of the needle tip in relationship to the neural foramen, and feedback that the needle tip is resting safely on bone.

After the needle tip is safely oriented on bone, the needle is withdrawn slightly and then redirected caudally and ventrally toward the target nerve root. The patient should be instructed to notify the operator as soon as he feels a paresthesia, which is elicited when the needle touches the nerve root. The needle should be targeted just dorsal of the uncinate process toward the center of the foramen; a fluoroscopic image confirms placement of the needle tip at or near the margin of the lateral mass adjacent to the targeted nerve, outside of the neural foramen and outside the epidural, subdural, and subarachnoid spaces.

Approximately 0.3 cc of a suitable contrast medium is carefully injected around the target nerve root. The contrast should outline the affected nerve root and produce a neurogram. Injection of 2-4% lidocaine should flow in the same distribution as the previously injected contrast. [19]

Both the contrast and local anesthetic irritate the target nerve root so that the patient experiences a painful response. If the purposed nerve root is the primary pain generator, then the patient experiences pain that is concordant. Concordance implies that provocation reproduces the essential nature of the neck and arm pain symptoms that are under investigation.

Also, as the LA takes effect, this familiar sensory experience, including pain characteristics (eg, intensity, regional pattern, associated symptoms) should diminish. This procedural approach is commonly referred to as provocate and ablate responses, and this approach is widely practiced by clinicians that may vary or determine their opinion based on the procedure's influence as a part of the data used to pursue and locate a spinal pain generator.


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